1. Field of the Invention
The invention relates generally to systems and methods for detecting key actuation in keyboard assemblies for information devices, and more particularly to systems and methods for detecting key actuation in keyboards for such devices.
2. Background Information
Small portable computers or xe2x80x9cpalmtopsxe2x80x9d can be conveniently carried in a purse or coat pocket. Recent advances in shrinking the size of electronic components will soon allow these devices to perform all the functions of today""s desktop computers. Additionally, a whole new category of xe2x80x9cinformation appliancesxe2x80x9d has begun. These include portable wireless telephone/computers which can be used to access the Internet to send and receive e-mail and to interact on the World Wide Web.
Powerful and versatile as these devices are becoming, their use is greatly limited by non-existent or inadequate keyboards. Palmtops which rely on handwriting recognition have proven to be awkward, slow and error prone. Miniature keyboards commensurate with the size of small appliances are likewise frustrating, especially if the user needs to write something consisting of a few sentences or more. Voice recognition suffers from frequent errors and creates a lack of privacy when other people are near the speaker whose voice is being recognized. Further, voice recognition may not be used in all circumstances (e.g. the process of taking notes of a lecturer""s lecture in an otherwise quiet auditorium may not be possible with voice recognition input systems but it is usually possible with a keyboard).
Keyboards for desktop and high quality laptop computers allow the user to comfortably, privately, quietly, and quickly xe2x80x9ctouch-type.xe2x80x9d They have a number of desirable features in common. Most keyboards have a standard xe2x80x9cQWERTYxe2x80x9d layout which requires no learning on the part of the user (once the user has become familiar with this layout). The keys, which usually number 84 for a laptop computer, have full-sized tops whose center-to-center spacing is about 19 mm for both the horizontal and vertical axes. The length of the keyboard (the distance from the left edge of the left-most key to the right edge of the right-most key) is about 11 inches. Any reduction in this spacing has proven to slow down and frustrate the touch-typist. Additionally, the keys of these keyboards have sufficient xe2x80x9ctravel,xe2x80x9d the distance the key moves when it is pressed, and tactile feedback, an over-center buckling action, that signals the user that the key has been pressed sufficiently.
Efforts have been made to provide keyboards that contain these features, yet collapse to a reduced size. Some designs only slightly reduce the size of xe2x80x9cnotebookxe2x80x9d computers when folded. These are much larger than palmtop computers. IBM""s xe2x80x9cThinkPad 701Cxe2x80x9d notebook computer folds in a single operation to reduce the keyboard case length (measured from the edges of its case) from 11.5 inches to 9.7 inches. Also see U.S. Pat. No. 5,543,787 which describes a foldable keyboard. U.S. Pat. No. 5,519,569 describes a keyboard which folds in multiple steps from a length of 10-11 inches to 6.125 inches. U.S. Pat. No. 5,654,872 describes a keyboard with keys that collapse when the lid is closed to allow a thinner notebook computer.
Other designs of keyboards include those where the keyboard is hinged at the center of its length and folds about a vertical axis. U.S. Pat. No. 5,457,453 describes a keyboard that folds to greater than half its length. U.S. Pat. No. 5,574,481 describes a keyboard that folds in half and appears to have a non-standard layout of keys (the keys on the center fold axis have edges which lie in a straight line). U.S. Pat. No. 5,653,543 describes a keyboard that folds in half. U.S. Pat. No. 5,502,460 describes a keyboard with two vertical hinges that folds to greater than half its unfolded length.
U.S. Pat. Nos. 5,044,798 and 5,141,343 describe keyboards whose keys have user-selectable variable spacing. These designs have non-standard layouts (e.g., the xe2x80x9cEnterxe2x80x9d key is rotated ninety degrees) and no self-containing housing. Their frame is made of telescoping sections that create a good deal of friction and could easily bind.
Keyboards electrically communicate information to information appliances. Most keyboards have printed circuit boards or membranes located underneath their keys. When a key is pressed it shorts the circuits in a particular column or row. The matrix of columns and rows that make up a keyboard is continually scanned by a controller to determine which keys have been pressed. Such an arrangement is described, for example, in U.S. Pat. No. 5,070,330. The electronic configuration of most keyboards thus necessitates a matrix of conductors that limits the collapsing of the keyboard to a certain size.
The present invention provides, in one example of the invention, a system and method for detecting key actuation in a keyboard assembly. In one embodiment, the keyboard assembly is a collapsible keyboard which includes a support element and a plurality of keys. The support element can be extended to provide a structure having a first footprint and contracted to a structure having a second footprint, where the second footprint takes less surface area than the first footprint. The plurality of keys are coupled to the support element. Each of these keys includes a key top, which is designed to be pressed by a user, and a key base which is coupled to the key top. The key top and the key base rotate, in one example of the invention, on a pivot point which couples the key base to the support element when the support element is extended and contracted.
In one exemplary embodiment, the invention provides detection of key actuation for a keyboard assembly that is capable of collapsing into its own protective housing. The housing consists of two symmetrical hollow box-shaped members, opened on one side. When closed, it forms a dust-proof enclosure surrounding a keyboard mechanism. When the keyboard assembly is in its collapsed position or state, it measures about 4.0-4.7 inches vertically (depending on the inclusion and height of xe2x80x9cfunctionxe2x80x9d keys), 3.25 inches horizontally, and 1.25 inches deep. In the collapsed state, the keyboard assembly can be carried in a purse or coat pocket along with a palmtop computer or other information appliance, such as a cellular phone. Its small size allows it to be conveniently stowed inside an appliance, such as a desktop telephone or television. When used with desktop computers or other information appliances, the collapsed state may be used to better utilize desk space when the computer is not in operation.
Expanding the keyboard from a collapsed state to a keyboard having conventionally spaced keys is done in a single step in one example of the invention. The user simply pulls the two halves of the protective housing apart. The housing remains attached, so it cannot be misplaced, and so the unit can be enclosed and protected in an instant. The housing may also include a cursor control device or a pointing device such as a touch-sensitive trackpad or joystick-like device such as IBM""s TrackPoint (found on IBM""s ThinkPad laptop computers). This cursor control device is, in one exemplary embodiment, selectively positionable on either the left or the right sides of the keyboard.
In one embodiment of the invention, key actuation detection is provided for a keyboard assembly having keys coupled to and supported by a support element which is a series of rows of multiple scissors-like, diagonally or X-shaped hinged linkages connected to the assembly housing. The linkages are selectively shaped such that any keyboard layout may be adopted, including the standard xe2x80x98QWERTYxe2x80x99 layout with its staggered columns and various width keys. The linkages also provide a. wide ratio of contraction, yet due to their diagonal shape when expanded, provide a strong and rigid structure. The hinged linkages create very little friction and do not require lubrication, so the keyboard assembly can be repeatedly opened and closed smoothly and easily. The keys are pivotally attached to the linkages, and by means of swing arms, pivot from a near vertical position, when the keyboard assembly is collapsed, to a horizontal position, when the keyboard assembly is expanded. To provide for a more compact profile when the assembly is collapsed, the keys are compressed to a closed and nesting position.
In one exemplary embodiment of the invention, the mechanical structure of the keyboard assembly is used as a conductor to electrically communicate with an information appliance. The rows are electrically insulated from one another, and each row contains keys bridging a two-wire bus. The rows are sequentially scanned by a controller. In another embodiment, each key has its own transponder circuit which identifies the particular key. When a key is pressed and the controller scans the row the key is in, the key""s transponder circuit indicates the identity of the key.
In another embodiment of the invention, the keys in each row of a keyboard assembly are arranged in two polarity groups by a diode coupled to each key. Each key in a polarity group has a different resistive load provided by a coupled resistor. Polarizing the keys allows the highest and lowest resistor values to define a reasonable range. Each key includes a key switch which is normally open and is closed when the key is pressed. When the switch is closed and the diode is biased with the current flow, the resistor will determine the resistive load of the pressed key. The keys in each row are coupled in parallel between two conductors.
In another embodiment of the invention, a keyboard assembly has rows of keys in which the keys in each row bridge two buses. Each key has a timer coupled to a switch and an electrical identifier, such as a resistor. The output of each timer goes high after a particular time period. When the switch is closed and the output of the corresponding timer is high, the electrical identifier provides an identifying load. A signal is sampled at different times to determine if the signal is changed by the identifying load. If so, a pressed key will be identified.
In yet another embodiment of the invention, a linear electrical matrix is coupled to a row of keys. The row is electrically separated into sections, each of which has its own section pathway for signals. Each key in each section is coupled to a key pathway, which is shared by corresponding keys in each section. Each row has its own set of section and key pathways, making the row appear electrically as if it were arranged in a matrix and allowing the rows to be electrically isolated from one another. In one embodiment, all sections are scanned concurrently to detect any responses from the keys. If a response signal is detected, the sections are scanned individually to identify the key that provided the response signal.
In still another embodiment of the invention, a two layer flexible circuit passes through each key assembly in a row of keys and provides the electrical pathways for a linear electrical matrix. The flexible circuit has an upper layer with a contact region disposed over the contact region of a lower layer. Conductive traces on each layer act as section and key pathways to allow signals to travel along the row of the keys. The flexible circuit is guided down between keys of a keyboard assembly, allowing the keyboard assembly to be collapsed more easily.
In one example of a method according to the invention, a row of keys is electrically separated into different sections. The different sections are then scanned sequentially to detect a key actuation signal that corresponds to a pressed key. A scan code corresponding to the key actuation signal is sent to a host computer.
Additional features and benefits of the invention will become apparent from the detailed description, figures, and claims set forth below.